Combine the cheesecake mix and cream cheese together in a bowl. Stir in some of sliced strawberries (save some for the top of the quesadillas). If using chocolate chips, add to mixture. Allow mixture to chill in the fridge for 2 hours. Spread 1/4 of the mixture on a tortilla, then top with another tortilla. Repeat until you have divided the mixture into 4 quesadillas. Butter the outside of each quesadilla. Cook each quesadilla in a nonstick pan until the outside of the tortillas are golden brown (about 3-4 minutes on each side). Add toppings and enjoy while hot!